Key points
- Typical 2026 market prices after STCs (incl. GST): about $26,000–$28,000 for 30 kW, $47,000–$49,000 for 50 kW and $77,000–$84,000 for 100 kW in Melbourne and Adelaide.
- For 30–100 kW systems that works out to roughly $0.77–$0.98 per watt, and the largest systems are cheapest per watt.
- STCs take about $27,000 off a 99 kW system in Adelaide and about $23,000 in Melbourne in 2026. From 1 October 2026 systems up to 1 MW can also claim STCs.
- Prices exclude extras such as network connection studies, protection equipment, ground mounting and meter changes. GST-registered businesses can usually claim the GST back.
Commercial solar cost in 2026 is roughly $0.80 to $1.00 per watt installed after the federal STC discount. In practice that means about $28,000 for a 30 kW system and $78,000 to $84,000 for a 100 kW system in Adelaide or Melbourne, based on the latest national price index. This guide breaks down what drives the price, what is usually left out of a quote, and how quickly a business system pays for itself.
How much does commercial solar cost in 2026?
The most consistent public price data comes from Solar Choice’s monthly commercial price index, which averages quotes from installers across Australia. These are the September 2026 averages for Adelaide and Melbourne. They already include the STC discount and GST.
| System size | Adelaide (avg, after STCs) | Melbourne (avg, after STCs) | Approx. $ per watt |
|---|---|---|---|
| 10 kW | $9,010 | $10,090 | $0.90–$1.01 |
| 30 kW | $28,060 | $26,150 | $0.87–$0.94 |
| 50 kW | $49,180 | $47,090 | $0.94–$0.98 |
| 70 kW | $65,990 | $62,180 | $0.89–$0.94 |
| 100 kW | $83,900 | $77,310 | $0.77–$0.84 |
Treat these as a guide, not a quote. Averages hide a wide spread. A simple tin roof with a big switchboard close by sits at the low end. A tile or flat roof that needs tilt frames, long cable runs, a switchboard upgrade or a crane sits at the high end. Panel and inverter brand, warranty terms and the installer’s overheads also move the price.
For a wider view of system sizing, incentives and network rules, see our complete commercial solar guide for Australian businesses.
What is included in a commercial solar price?
A standard commercial quote usually covers:
- Tier 1 or CEC-listed panels (typically 440–475 W each in 2026)
- One or more three-phase inverters
- Racking and roof fixings for a standard pitched metal roof
- DC and AC cabling, isolators and switchboard work
- Monitoring, commissioning and compliance paperwork
- Creation of the STCs on your behalf, shown as a discount on the invoice
The Solar Choice index specifically excludes meter installation fees, ground mounting, grid protection and grid connection studies. Those are the items that most often surprise business owners, so ask for them to be listed separately.
Extras that can add to the cost
- Network application and assessment fees. In SA, inverter systems above 30 kVA go through SA Power Networks’ medium embedded generation process, which involves an application fee, a network assessment, a connection contract and witnessing of the commissioning. Victorian distributors also treat systems above 30 kVA as negotiated connections with additional costs.
- Protection and export control. Larger systems may need grid protection relays, export limiting or remote monitoring equipment.
- Tilt frames or ballast for flat roofs, and engineering reports for older or lightweight roofs.
- Switchboard upgrades where the existing board has no space or is not rated for the new load.
- Access equipment such as scissor lifts, cranes or edge protection for high roofs.
Tip: Ask every installer to quote on the same basis: the same system size, the network costs shown separately, and prices both including and excluding GST. That is the only way to compare quotes fairly. Our guide on how to compare solar quotes has a full checklist.
How much do STCs take off a business system?
Small-scale technology certificates (STCs) are the federal incentive behind the “after STCs” prices above. The number of STCs depends on system size, your location’s zone rating and the deeming period, which is 5 years for systems installed in 2026. Adelaide is in Zone 3 (1.382) and Melbourne in Zone 4 (1.185).
| System size | STCs in Adelaide (2026) | Approx. value | STCs in Melbourne (2026) | Approx. value |
|---|---|---|---|---|
| 20 kW | 138 | $5,500 | 118 | $4,700 |
| 30 kW | 207 | $8,200 | 177 | $7,100 |
| 50 kW | 345 | $13,700 | 296 | $11,800 |
| 99 kW | 684 | $27,300 | 586 | $23,400 |
Values use an STC price of about $39.85, close to the early October 2026 spot price. Your installer’s actual discount may be slightly lower to cover their costs.
The big change this year is that systems from 100 kW up to 1 MW can now claim STCs too, if installed from 1 October 2026. Before that, systems over 100 kW could only earn smaller, ongoing large-scale certificates. We explain the new rules, and why 99 kW systems are still common, in our post on the commercial solar rebate now covering systems up to 1 MW.
Worked example: what does a 30 kW system return?
Take a workshop in Adelaide’s northern suburbs that runs Monday to Friday, 7am to 4pm.
- Price: about $28,000 including GST, or about $25,500 excluding GST if the business claims the GST credit.
- Generation: Adelaide averages roughly 4.2–4.4 kWh per kW per day, so 30 kW makes around 47,000 kWh a year.
- Self-consumption: if 70% is used on site during working hours, that is about 33,000 kWh not bought from the grid.
- Savings: at an assumed 25c/kWh daytime rate (check your own bill), that is about $8,200 a year, plus a small amount for exported solar.
On those assumptions the simple payback is around 3 years, before any tax depreciation benefit. In Melbourne, generation is lower (about 3.6–3.8 kWh per kW per day) so the same system makes around 40,000 kWh a year and pays back a little more slowly. Our general guide to the solar payback period in 2026 walks through the method in more detail.
The key variable is how much solar you use on site. A business that is closed on weekends exports two days in seven unless it sizes the system carefully or adds storage. Retail feed-in tariffs for business are low, so exported energy is worth far less than energy you use.
Which system size gives the best value?
Bigger systems are cheaper per watt, but that does not mean bigger is always better. The best value is the largest system whose output you can mostly use during the day, within your roof space and network limits.
- 20 kW: small offices, cafes and retail with steady daytime use.
- 30 kW: medical centres, gyms, larger shops. Our 30kW commercial solar system page shows a typical layout and output.
- 50 kW: workshops, light manufacturing, childcare centres.
- 99–100 kW: warehouses, cold storage, wineries and farms with high daytime loads. See our 99kW commercial solar system package.
- Over 100 kW: now eligible for STCs up to 1 MW, worth modelling for large sites with big daytime demand.
Ask for 12 months of interval meter data from your retailer or distributor. It shows exactly when you use power and is the best way to size a system for a fast payback.
How do batteries and tax change the numbers?
Adding a battery raises the upfront cost but can cut evening use and peak demand charges. Small businesses can access the federal battery discount on batteries from 5 to 100 kWh, at 6.8 STCs per usable kWh for installs until 31 December 2026. Whether a commercial battery storage system pays off depends mainly on your load after 5pm and on how your network charges for demand.
On tax, a solar system is a depreciating asset. Most commercial systems cost more than the $20,000 instant asset write-off limit, so small businesses usually add them to the small business pool. Our guide to commercial solar tax depreciation explains how that works. Always confirm the treatment with your accountant.
How can you keep commercial solar costs down?
- Size to your daytime load, not your roof. Oversized systems export more energy for little return.
- Use the roof you have. Metal roofs facing north, east or west are the cheapest to install on.
- Bundle switchboard work into the solar project instead of doing it separately later.
- Get network costs early. For systems above 30 kVA, ask for the network application to be lodged before you commit to the final design.
- Check finance options. Interest-free plans, equipment finance and green loans can turn savings into positive cash flow from month one.
Frequently asked questions
How much does a 100kW commercial solar system cost in 2026?
The September 2026 Solar Choice index puts the average at about $83,900 in Adelaide and $77,300 in Melbourne, after STCs and including GST. Expect extra costs for network studies, protection equipment or difficult roofs. Systems over 100 kW installed from 1 October 2026 can also claim STCs.
Do commercial solar prices include GST?
Published index prices usually include GST. A GST-registered business can normally claim the GST back as an input tax credit, so the real cost is about one-eleventh lower. Ask installers to show prices both including and excluding GST so you can compare quotes properly.
What is the payback period for commercial solar?
On assumptions like our worked example, well-sized systems in Adelaide and Melbourne can pay back in roughly 3 to 6 years. The main drivers are how much of the solar you use on site, your daytime electricity rate and the installed price. Businesses that operate seven days a week usually see the fastest payback.
Are there hidden costs in commercial solar quotes?
The most common extras are network application and assessment fees for systems above 30 kVA, protection or export control equipment, switchboard upgrades, tilt frames for flat roofs and access equipment such as cranes. A good quote lists these separately instead of leaving them out.
If you would like a clear, itemised price for your site, our Adelaide and Melbourne team can model your interval data and design a system around how your business actually uses power. Get a free commercial solar quote.
Sources: Solar Choice – Commercial Solar Panel Prices, September 2026 (1 Sep 2026); Clean Energy Regulator – Mid-scale solar (updated 7 Oct 2026); SA Power Networks – Medium embedded generation; Jemena – Solar installers hub. Prices are market averages, not Solar Beat prices, and STC values change daily. Featured image: MassDOT / Wikimedia Commons, Public domain.
